1. Field of the Invention
The present invention relates to a sheet processing device performing a process such as a sheet saddle-stitching process and an image forming system including the sheet processing device.
2. Description of Related Art
Conventionally, devices have been used that perform a sheet processing including sheet center-folding process and sheet saddle-stitching process.
Japanese Patent Application Laid-Open No. 2005-96913 discloses technology that changes the posture of a sheet, and then performs a center-folding process and a saddle-stitching process. In Japanese Patent Application Laid-Open No. 2005-96913, a manner of changing the sheet posture so as to achieve rapid and reliable changes in sheet posture with respect to various sheet sizes has been proposed.
Japanese Patent Application. Laid-Open No. 2006-36402 discloses a device that achieves feeding of a pile of sheets placed on a saddle while preventing feeding troubles or crinkles even when the pile includes a large number of sheets.
On the other hand, the device disclosed in Japanese Patent Application Laid-Open No. 2005-96913 changes the posture of a sheet three times. Accordingly, because a mechanism for changing the posture of the sheet is complicated and extra space is required to change the posture of the sheet, it is thought that the device is more susceptible to increase in size.
The device disclosed in Japanese Patent Application Laid-Open No. 2006-36402 lifts up the pile of sheets (booklet) that have been saddle-stitched on the saddle and feeds the pile of sheets to a subsequent processor. Such a configuration requires a complicated mechanism for feeding the pile of sheets, resulting in complication and an increase in the size of the entire device.